Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/06—Lenses; Lens systems ; Methods of designing lenses bifocal; multifocal ; progressive
  • G02C7/061—Spectacle lenses with progressively varying focal power
  • G02C7/068—Special properties achieved by the combination of the front and back surfaces
• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/024—Methods of designing ophthalmic lenses
  • G02C7/027—Methods of designing ophthalmic lenses considering wearer's parameters
• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
  • G02C7/06—Lenses; Lens systems ; Methods of designing lenses bifocal; multifocal ; progressive
  • G02C7/061—Spectacle lenses with progressively varying focal power

Definitions

• the present invention relates to the production of an ophthalmic lens for a pair of spectacles which is intended for an identified wearer.
• a so-called "progressive" ophthalmic lens presents a variation in optical power when a wearer of this lens looks successively through a far vision zone and a near vision zone of the glass.
• This variation in optical power results from variations in the curvature of at least one of the front and rear faces of the glass.
• optical power defect and astigmatism it is also known to adapt the distribution of an optical power defect and astigmatism according to a propensity of the wearer to move rather the eyes or the head when looking successively in different directions. It then characterizes the eye movement and head movements of the wearer, then we choose according to them a glass design that provides comfort superior to the wearer.
• the width of the far (or near) vision zone of the glass corresponds to the horizontal interval, for the standard position of use of the lens by the wearer, around the distant (near or far) vision point. in which the optical power failure and / or astigmatism remains imperceptible " or below a fixed threshold.
• a progressive lens can thus be attributed to each wearer, which gives him a good comfort whatever is his behavior of eye or head wanderer.
• An object of the present invention is therefore to provide a progressive lens which is dedicated to a wearer, and which brings him increased comfort.
• the object of the invention is to reduce the duration of the period of habituation that can be felt by the wearer of the glass.
• the object of the invention may be to reduce a pitching sensation that is sometimes perceived by the wearer when he has been using a progressive lens for a short time.
• the invention proposes a method for producing an ophthalmic lens for a pair of spectacles which is intended for an identified wearer, the lens having an anterior face and a posterior face each having an addition, which process comprises the steps following:
• a method according to the invention is characterized in that it further comprises the following steps:
• step 121 selecting addition values which are respectively for the anterior and posterior surfaces of the glass, which values the two faces are adapted so that the glass has substantially the prescribed addition value, and so that the characteristic which is determined in step IZI is adapted to the wearer;
• the addition values of the front and rear faces of the glass are selected not only so as to obtain substantially the addition value of the glass which is prescribed, but also to adapt a characteristic of use of the glass depending on the movements of the eyes and head of the wearer.
• This adaptation of the characteristic of use of the glass corresponds to a personalization of the glass. It is performed to improve a feeling of the wearer who intervenes when changing direction of gaze. In this way, a comfort of use of the glass is obtained, which is increased.
• the characteristic that is determined in step / 3 / may be a variation of a magnification for different directions of gaze of the wearer to through the glass. This variation of magnification is then selected according to the perception of the wearer, to provide him with increased comfort.
• step IAI Variations in magnification that are felt by the wearer can cause him an inconvenience, such as a pitching sensation or even a disturbance of the balance.
• the respective addition values of the anterior and posterior faces of the glass can then be selected in step IAI so as to reduce these magnification variations when the relative amplitude of the wearer's head movements which is characterized in step 121 is more large, compared to variations in magnification that would be obtained for a lower relative amplitude of head movements, for a prescription in far vision and in addition that are identical.
• the variation of magnification can be considered between two directions of view of the wearer who cross the glass respectively at the far vision point and the near vision point.
• the pitching impression that is due to the difference in magnification between the near vision zone and the far vision zone is all the more accentuated as the wearer moves mainly the head, rather than the eyes:
• magnification can be reduced by using the invention for these carriers.
• the magnification of the lens in the near vision zone can be increased.
• the addition value that is selected for the anterior face of the lens may be smaller when the relative amplitude of the wearer's head movements is greater, compared to an addition value of the anterior face that would be selected for a lower relative amplitude of the head movements, for a prescription in far vision and in addition value for the glass which are identical.
• FIGS. 1a and 1b are respectively front and side views of a spectacle lens according to the invention
• FIGS. 2a and 2b illustrate a principle of measurement of eye and head movements for a spectacle wearer
• FIG. 3 is an example of a table indicating the addition values of the front face of the glass, selected according to the present invention.
• FIGS. 4a and 4b are respectively spherical and cylindrical maps of the front face of a first spectacle lens made according to the invention, and intended for a first wearer who moves the eyes more than the head;
• FIGS. 4c and 4d are respectively maps of sphere and cylinder of the posterior face of the first lens of FIGS. 4a and 4b;
• FIG. 4e is an optical power characterization of the first lens of FIGS. 4a to 4d;
• FIGS. 5a to 5e respectively correspond to FIGS. 4a to 4e, for another spectacle lens made according to the invention, and intended for a second wearer who moves the head more than the eyes;
• the invention is now described in detail in the context of producing corrective ophthalmic lenses such as spectacle lenses. But it is understood that the invention can be applied to other ophthalmic components that perform a correction of a visual defect, such as glasses of mountain masks or aquatic diving in particular.
• spectacle lenses that are adapted to perform a presbyopia correction are taken as examples. But it is also understood that the invention can be applied in a similar manner to any corrective glass, whatever the nature of the visual defect of the wearer, since the faces of the glass may have variable curvatures. In addition, any correction of astigmatism can be superimposed in known manner to the power prescription which is discussed alone in the following.
• the correction that is prescribed to a future presbyopic spectacle wearer comprises at least one optical power value which is determined under far vision conditions, and an addition value of the lens.
• the optical correction power that is necessary for the wearer in near vision is then equal to the value of the optical power prescribed for the far vision increased by the prescribed addition value.
• the glass is then made to present substantially these optical power values at two points which are respectively located in the viewing zone. by far and in the near vision area. These points are called far vision point and near vision point. In Figure 1a, they are denoted VL and VP respectively.
• the reference 1 designates the glass and the letter O designates the center of the glass. This center O is also commonly used as a prismatic reference point for glass.
• VL is located on a vertical line above O, and VP is shifted laterally (parallel to the X axis) with respect to VL.
• the VP shift direction is reversed between a right and a left lens.
• a line M which is called the main meridian line, connects the points VL and VP. It corresponds to the trace on the glass of the gaze direction when the wearer successively observes objects which are situated in front of him at varying heights and distances.
• Figure 1b shows the front and rear faces of the glass.
• S P OST- Glass 1 can be made of any transparent material that is compatible with the ophthalmic application.
• this material can be mineral, organic or composite.
• the points O, VL and VP are defined on the anterior face SANT of the glass 1, and serve as reference points for evaluating the sphere of this anterior face in order to determine the addition AANT of the latter.
• the APOST addition of the posterior surface SPOST of the glass 1 is determined from sphere values which are evaluated at two points of reference of this posterior face which correspond to the points VL and VP. These two reference points of the posterior face may be located respectively vis-à-vis points VL and VP, or be shifted relative thereto along the path of light rays that pass through points VL and VP .
• the reference points of the posterior face can be defined from points VL and VP using various light path approximations.
• the relative magnitudes of eye and head movements made by the wearer to whom the glass is intended are then characterized.
• a first target called reference target
• the reference target is denoted R in Figure 2a, and the reference number 10 designates the carrier. It can be located at eye level for the wearer, in particular. The wearer is therefore placed in front of the reference target, with the shoulders substantially located in a vertical plane which is perpendicular to the virtual line that connects his head to the reference target. He then has his head and his eyes oriented towards the reference target.
• test target and noted T which is shifted relative to the reference target, without moving the shoulders.
• the wearer is asked to look at a second target, called test target and noted T, which is shifted relative to the reference target, without moving the shoulders.
• the test target is horizontally offset from the reference target, so as to characterize the horizontal movements of the wearer's head and eyes.
• the angular offset of the test target relative to that of reference is called eccentricity, and denoted E.
• ⁇ r denotes the angle of rotation of the wearer's head, also called angular deflection of the head, to move from the first observation situation of the reference target to the second situation of observation of the test target
• ⁇ y is the angle of rotation of the eyes that is performed simultaneously by the wearer.
• the eccentricity E is therefore equal to the sum of the two angles Or and ⁇ y.
• the quotient of the angular deviation of the head ctr is then calculated by the eccentricity E. This quotient is equal to unity for a wearer who has exclusively turned his head to pass from the reference target to the test target, and to zero for a wearer who has only turned his eyes.
• a G gain is then calculated for this "eye / head" motion coordination test that has been performed for the wearer.
• the gain G can be defined by a predetermined function of the quotient of the angular deviation of the head OT by the eccentricity E.
• This "eye / head” movement coordination test can be performed by the wearer in the shop of an optician retailer where he orders his pair of glasses equipped with corrective glass.
• Other "eye / head” motion coordination tests that are equivalent to the one just described can be be carried out alternately, without the implementation of the invention being modified in principle.
• the invention is described in the following by adopting the variation of the apparent magnification of the glass as a characteristic of adaptation of the glass to the carrier, via the selection of the addition values of the anterior face and the posterior face of the glass.
• This magnification is produced by the lens when it is fitted into a spectacle frame and placed on the wearer's face for given conditions of use. It is equal to the quotient of the size of the retinal image with corrective lens by the size of the retinal image without glass.
• This magnification, noted SM for Spectacle Magnification
• D 1 denotes the curvature of the anterior face of the glass at the crossing point of the light beam
• D is the optical power of the glass at the same point
• e is the thickness of the glass at the center O of the latter (see Figure 1b)
• n is the refractive index of the material that composes the glass between its two faces
• d is the distance between the posterior surface of the glass and the entrance pupil of the eye.
• R1ANT and R2 A NT respectively designate the minimum and maximum radii of curvature of the anterior face in two directions perpendicular to each other. They are determined at the far vision point VL or at the near vision point VP according to the indication which appears in index of each parenthesis inside the hook, n further denotes the refractive index of the glass material.
• the final addition of the glass results from a combination of the respective additions of the anterior and posterior sides.
• the skilled person speaks of distributing the addition of glass A between the two faces of the glass.
• the table below shows the characteristics of five progressive glasses, all of which correspond to the same prescription: sphere and cylinder void in far vision, and prescribed addition of 2 diopters.
• the table also indicates the values of the magnification SM at the points of vision of far and near.
• the SANT anterior face is first selected from a series of available anterior faces. This anterior face has the addition value AANT- Then the posterior face SPOST is calculated to obtain, when combined with the selected front face, a value of the actual addition of the glass which is close to the value A, and to obtain at the same time an optical power value at the far vision point which is close to the corresponding prescribed value.
• magnification values SMVL and SMyp are calculated using the formula 1 at the far vision points VL and near VP, with values of the curvature Di which are determined for the selected front face, and optical power values D which are determined for the combination of the selected anterior surface and the calculated posterior surface.
• the last column of Table 1 indicates the type of carrier for which each of the five glasses is preferably intended, depending on the value of gain G that is obtained on the "eye-head" motion coordination test. From the value of the gain G which has been determined for an identified carrier, several methods can be used to select the addition values A A NT and APO S T ' respectively of the anterior face SANT and of the posterior face S P OST of glass, while maintaining substantially constant the addition of glass. Among these, we can mention:
• a mathematical formula which relates a distribution parameter of the addition of the glass between the anterior and posterior faces on the one hand, and the calculated gain on the other hand.
• This formula may correspond in particular to a continuous function which determines the distribution parameter from the gain and, optionally, from the prescribed addition value of the glass.
• a A NT / A ⁇ (k-G + m) where k and m are two constants fixed initially.
• the addition value AANT which is selected for the front face of the glass may be less than the addition value of the glass A which is prescribed for the wearer.
• the addition that is selected simultaneously for the posterior face is then positive.
• the table of FIG. 3 indicates such a selection, at least when the relative amplitude of the head movements of the wearer is greater than or equal to the corresponding relative amplitude of the eye movements, that is to say when G> 0.5, and when the addition A of the glass that is prescribed for the wearer is greater than or equal to 1 diopter.
• the addition A A NT of the anterior face may be greater than the prescribed addition.
• the skilled person then speaks of over-addition of the anterior face of the glass and the addition of the posterior face is then negative, to compensate for this over-addition.
• the glass 1 of Table 1 above corresponds to such a case of over-addition of the anterior face.
• the glass can then be manufactured in a customary fashion, with the anterior and posterior faces having the selected additions and far-sighted point bends that are appropriate to the prescription.
• a semi-finished glass model can be selected, which has a definitive anterior face corresponding to the addition AANT and which is compatible with the prescription.
• the posterior face is then machined in recovery to obtain the AP O ST addition and prescription.
• Figures 4a and 4b are respective maps of the sphere and cylinder values of the anterior face SANT of the glass 1 which is indicated in Table 1. These figures together characterize the design of this face. They are limited by the circular edge of the glass, and each point of the face is marked by two rectangular coordinates, respectively denoted X and Y, and expressed in millimeters (mm).
• the lines shown in Figure 4a are isosphere lines, which connect points on the face of the glass that correspond to the same sphere value. This value is indicated in diopters for some of these lines.
• the lines shown in Figure 4b are isocylinder lines, which connect points on the face of the glass that correspond to the same cylinder value.
• the sphere which is also called medium sphere
• the cylinder of the anterior face of the glass at a point of it are given by the following formulas: Cyl ANT (4b)
• the far and near vision points, VL and VP are located on the maps 4a and 4b.
• the difference in sphere values between the points VP and VL corresponds to the addition of the anterior face, which is equal to 3.02 diopters (FIG. 4a).
• CM An additional point, noted CM and called cross mounting glass, is also indicated as a reference on these maps.
• the point CM is the point of the glass which must be placed in front of the center of the pupil of the wearer for whom the glass is intended.
• Figures 4c and 4d are similar maps for the posterior surface SPOST of the glass 1, respectively sphere and cylinder. The addition of the posterior face of the glass 1 is equal to -0.98 diopters.
• Figure 4e illustrates the variations of the optical power of the glass 1.
• Each direction of observation through the glass is marked by two angular coordinates expressed in degrees: alpha locates the observation height with respect to a horizontal plane, and beta marker the rotation of the eye in this horizontal plane.
• the directions corresponding respectively to the points VL and VP are also indicated on this map.
• the lines indicated in FIG. 4e are isopower lines, which connect observation directions through the glass which correspond to the same optical power value. This value is indicated in diopters for some of these lines.
• the power of the visual correction is substantially zero at the far vision point VL, and equal to 2.28 diopters at the near vision point VP.
• the glass 1 therefore has an addition close to the prescribed value of 2.0 diopters.
• FIGS. 5a to 5e similarly characterize the glass of Table 1.
• a comparison of FIGS. 4e and 5e show that these glasses have optical functions which are substantially identical, whereas they have magnification values SM at the point of vision from near VP who are different (see Table 1).
• the manufacture of the final glass from a semi-finished glass comprises the following preliminary steps:
• a fictitious target lens by associating the mating anterior face with a fictitious posterior face, the latter having uniform values of sphere and cylinder selected so that the fictitious target lens has an optical power at the far vision point which is substantially equal to the value prescribed for the holder;
• the front face of the semi-finished glass initially selected has a medium design, which is intermediate between a design to wide viewing areas and a design with narrow viewing areas. In this way, it has moderate sphere and cylinder gradients.
• the posterior face of the semifinished glass which was initially selected is then produced, for example by machining, in accordance with the posterior face of the hypothetical optimized test lens. It is understood that, depending on the optimization program that is used and the particular case of each lens made, the optimized test dummy lens may have characteristics that are not strictly equal to those of the dummy target lens. Those skilled in the art will understand the meaning of the term "substantially equal optical characteristics" in that the gap between the dummy test lens and the target dummy lens is reduced by the optimization step.
• This improvement makes it possible to adapt to the wearer, according to its propensity to turn rather the head or eyes, not only the distribution of the addition between the two faces of the glass, but also the design of the glass.
• the adaptation of the design is achieved via the posterior surface of the glass only, which makes it possible to use only one model of semi-finished glass for all the glass designs that are finally obtained.
• the range of semi-finished glasses that is required to make ophthalmic lenses for any carriers using the invention need not contain patterns that are differentiated only by the anterior-face design.
• the management of stocks of semi-finished glasses is then simplified.
• each model of semi-finished glass can be manufactured in larger series, which reduces its cost per unit.
• the reference gain values that are used may respectively correspond to a first wearer who would only turn his eyes during a change of direction look, and a second carrier who would turn only the head at the same change of direction of gaze. They therefore correspond to two extreme behaviors of the wearer, so that the anterior face of the target fictitious lens is then intermediate between the two anterior reference faces.
• the mixture of the two reference front faces to obtain the anterior face of the target dummy lens can be performed by characterizing each reference face by its sagittal values ("sag value" in English) at the points of a common mesh. defined on them.
• the sagittal values of the two reference faces are then added to each other, for each point of the mesh, by weighting them by coefficients which are determined appropriately.
• the gains are equal to the quotient of the deflection of the wearer's head by the eccentricity of the test target, the values of the gain which serve as a reference are zero and unity.
• the mixture of the reference faces can then be performed by applying the following linear combination to the sagittal heights, for each point of the mesh:
• S AN ⁇ (carrier) denotes the anterior face of the calculated target dummy lens for the wearer
• G is the value of the gain which is calculated for the latter
• the two prior reference faces are each mixed with a linear combination coefficient which is proportional to the difference between the corresponding reference gain value and the calculated gain value for the wearer. It is understood that other surface mixing rules which are equivalent to formula 6 can be used alternately, in particular according to the gain scale which is adopted for the motion coordination test.
• the sum of the two linear combination coefficients which are respectively assigned to the two reference front faces, for the same point of the mesh, is preferably equal to unity. These coefficients may also vary between different points of the mesh, to change a preponderance of one of the two reference faces in the mixture, within certain areas of the front face of the glass.
• the optimization of the dummy test lens with respect to the target dummy lens can be performed by initially assigning to the dummy test lens a backside which is corrected for a gap between the anterior face of the semi-finished lens and the anterior face of the fictitious target lens. This correction is applied with respect to an initial imaginary posterior face which is spherical or toric, that is to say which does not present an addition by itself.
• a subtraction of surfaces designates a combination operation of two initial surfaces to obtain a third, by which a sagittal value of the second surface is subtracted from that of the first surface, each point of the common mesh, and the third surface is defined by assigning the result of the subtraction as the new sagittal height at the same point.
• the optimization is done iteratively using a merit function to measure a gap between the dummy test lens that is obtained at each iteration and the target dummy lens, the optimization requires a lower number of times. iterations to achieve the same value of the merit function.
• the imaginary target lens can also be defined with a base value of the anterior face different from that which would be selected for the semi-finished lens according to the prescribed vision correction, in particular as a function of the power value. optics that is prescribed for the wearer and for far vision. In this way, optical aberrations of the final ophthalmic lens can be minimized.
• FIGS. 6a, 6b, 7a, 7b and 8a, 8b relate to a sixth glass, denoted glass 6, which has been made according to the improvement which has just been described.
• This lens 6 still corresponds to a prescribed addition of 2.0 diopters and zero optical power at the far vision point. It is intended for a zero-gain wearer, like the glass 1 of Table 1.
• FIGS. 6a and 6b are characterizations of the anterior face of the series semi-finished glass that has been used to make the glass 6.
• This semi-finished glass has an anterior face addition which is equal to 3 diopters, in accordance with FIG. implementation of the invention.
• FIGS. 7a and 7b are respective optical power characterizations of the fictitious initial test lens and the target fictitious lens, such that these were used during the production of the glass 6.
• the addition of these different fictitious glasses is substantially equal to 2 dioptres, according to the prescription of the wearer.
• astigmatism values are used for the dummy test lens and the target dummy lens together with the optical power values, especially for the step optimization.
• Figures 8a and 8b are optical power characterizations and resulting astigmatism that were performed for the glass 6 finally obtained.
• FIGS. 9a and 9b are optical power and residual astigmatism characterizations which have been carried out for a seventh glass, denoted as glass 7.
• the glass 7 has also been produced according to the improvement of the invention, but being intended for a winning carrier equal to unity. It therefore corresponds to a prescription which is identical to that of the glass of Table 1, with the same additions of the anterior and posterior sides, respectively. But it results from an additional optimization of the design, made for a wearer who turns only the head.
• FIGS. 8a and 9a on the one hand, and 8b and 9b on the other hand show that the near and far fields of view of the glass 6 are wider than those of the glass 7. At the same time, the gradients of The optical power and astigmatism of the glass 7 are lower than those of the glass 6, for identical viewing directions.
• the realization, according to the improvement of optimization of the design, of an eighth glass corresponding to the data of the glass 3 of Table 1, has resulted in a design which is intermediate to those of the glasses 6 and 7,

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